This invention relates to a monitoring device for receiving, displaying, and monitoring serial data flowing through a serial transmission line.
In investigating transmission error, prior art monitoring devices make use only of data usually displayed on a display device such as a CRT or a flat panel display. Thus, in investigating transmission error which may occur in devices or systems associated with the serial transmission line (i.e. in operation or in preparation of such devices or systems), it is difficult to clarify error sources since data preceding and/or following the usually displayed data can not be given. If such preceding and/or following data could be displayed in addition to the transmission data portion usually displayed, the analysis of error source would become more reliable.
Modern improvements of transmission protocol has resulted in a trend toward use of complicated transmission sequences. With use of these complicated transmission sequences comes the possibility that error source may initiate in a greater possibility of places within the system: e.g. at the transmitting site, at the receiving site, in mutual data transmission sequences between the transmitting and receiving sites, data transmitted and received under specific conditions, etc. The present invention addresses this problem by making possible the analysis of different transmission sequences via a break function which terminates a data display in response to, an occurrence of a specific data. However, it is still difficult to analyze the transmission sequence with only the addition of a break function.
Since the display unit will not discriminate between data whose break condition is established and data whose break condition is not, it becomes difficult to search for the transmission data whose break condition is established. Furthermore, when a plurality of trigger data whose break conditions are established exist on the display screen, the search becomes more difficult.
Thus it would be advantageous to have the display indicate or distinguish data whose break condition has been established.
In order to further facilitate analysis of a transmission sequence, it would be advantageous to make it possible to display a portion of data following the transmission data in which an error occurs. Further, it would also be advantageous to make a monitoring device where it is possible to have a function for analyzing data, wherein the break condition can be arbitrarily changed based upon the content of the data stored in a memory of the monitoring device.
In analyzing the content of transmission data monitored, it is conventional to display the data in real time on a display device. It may be desirable to record the transmission data by using an inexpensive cassette tape recorder so that it can be reproduced at any later time. This is particularly advantageous when the system and associated devices are to be field-checked and thus it would be impractical to immediately identify an error therein. That is, in such case, it is necessary to not only display the data in real time, but also simultaneously record it by a recording device such as cassette tape recorder. Such recording device should be as compact and easy in handling as possible.
However, it is difficult to record transmission data transmitted at a speed as high as, for example, 19.2K bits/second by using a cassette tape recorder. As a result, the reliability of reproductions from reproduced data may be poor. Again, this is an increasing problem because of a speeding-up of transmission due to a recent substantial improvement in serial transmission methods.
With the increase of data transmission rate, it also becomes difficult to perform simultaneous control of an external display device and data setting with respect to an external memory. In order to realize the simultaneous display and recording with using an inexpensive memory device, it may be possible to store the transmission data temporarily in a random access memory, and then to simultaneously display and record it later by using the content of the memory. This approach, however, requires an increased processing time, causing time delays in supplying display output to a display unit and memory output to a simple memory unit such as cassette tape recorder.
Once a serial data on the serial transmission line is received and then displayed on the display unit such as CRT to monitor it, prior art devices are also disadvantageous in that it is difficult to determine the direction of data displayed, i.e. there are at least two data directions. One being sent from the transmitting side to the receiving side and the other being opposite in direction. In order to determine the data direction one approach would be to display them separately. However, although the mere separate display of the transmitting and the receiving side data may facilitate an analysis of simple transmission conditions, it is still difficult to analyze complicated time serial data transmission conditions (e.g. time from an end of the transmitting side data flow to a start of the receiving side data flow, time delays introduced in these data flows, etc.).
Separate display of transmitting and receiving data also has a further disadvantage. When display and monitoring is made of the transmitting data only, the display screen area for receiving data remains empty. The opposite is true when display and monitoring is made of the receiving data only. Thus, an approach using separate display of transmitting and receiving data is inefficient as to use of display screen area.
A further disadvantage of the prior art is observed in the monitoring of data in a semi-duplex system. In display of data transmission in a semi-duplex system, it is usual to display only transmitting and receiving side data in which protocol such as flags, characters, etc. have been removed. This removal before display makes it impossible to analyze possible errors in protocol in the semi-duplex transmission system. Thus it would be advantageous to be able to display these protocol to facilitate analysis.